381 research outputs found

    Estudio de los corales con aulos del Viseense (Carbonífero) de la Unidad de la Sierra del Castillo (Área del Guadiato, SO de España)

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    Se describen los corales rugosos con aulos del Viseense del Área del Guadiato (Ossa-Morena). Los corales proceden de las localidades de Sierra del Castillo (secciones del Collado y la Cantera), Sierra de la Estrella (ambas en el término de Espiel) y de Peñarroya. En ellas de han identificado tres especies pertenecientes a dos géneros, Solenodendron furcatum, Solenodendron horsfieldi y Aulokoninckophyllum carinatum. Las características microestructurales del género Solenodendron se describen por primera vez. Las diferencias microestructurales entre Solenodendron y Aulokoninckophyllum permiten suponer un origen diferente para los dos géneros, lo que vuelve a plantear el polifiletismo de este grupo. Las especies Solenodendron horsfieldi y Aulokoninckophyllum carinatum se describen por primera vez en España. [ABSTRACT] Viséan rugose corals with aulos are studied in this paper. Corals are recorded in four localities from three different areas (Sierra del Castillo, Sierra de la Estrella and Peñarroya) at the Guadiato Area (Ossa Morena). Three species belonging to two genera have been identified and described in detail: Solenodendron furcatum, Solenodendron horsfieldi and Aulokoninckophyllum carinatum. Aulokonickophyllum carinatum and Solenodendron horsfieldi are recorded for the first time in Spain. Microstructural features of Solenodendron are described for the first time. Solenodendron possesses septa with fibrous (water jet) microstructure. On the contrary, Aulokonickophyllum shows trabecular microstructure of the septa in the dissepimentarium. The trabeculae are disposed as a fan system. When the septa reach the tabularium the trabeculae are substituted by fibrous microstructure with water-jet disposition. Microstructural differences between Solenodendron and Aulokonickophyllum allow to propose different evolutive origin for these two genera

    Estudio de los corales cyathópsidos (Rugosa) del Viseense superior de la Unidad de la Sierra del Castillo (Córdoba, España)

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    Los corales rugosos con disepimentos son frecuentes en la Unidad de la Sierra del Castillo, que comprende materiales predominantemente carbonatados del Viseense superior del Área del Guadiato (Ossa-Morena). Se han estudiado los cyathópsidos de la Sierra del Castillo, de la Sierra de la Estrella (ambas en el término de Espiel, Córdoba) y los de la zona de Antolín (en el término de Peñarroya, Córdoba) en las que se han identificado 7 especies pertenecientes a 5 géneros (Siphonophyllia, Caninia, Pseudozaphrentoides, Haplolasma y Caninophyllum). [ABSTRACT] Dissepimented rugose corals are frequent in the Sierra del Castillo Unit (Guadiato Area, Ossa Morena) which is composed mainly of Viséan limestones. Cyathopsid corals from Sierra del Castillo, Sierra de la Estrella (both near Espiel, Córdoba) and Antolín (near Peñarroya, Córdoba) have been studied. Seven species belonging to the genera Siphonophyllia, Caninia, Pseudozaphrentoides, Haplolasma and Caninophyllum have been described

    Policies and Motivations for the CO2 Valorization through the Sabatier Reaction Using Structured Catalysts. A Review of the Most Recent Advances

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    The current scenario where the effects of global warming are more and more evident, has motivated different initiatives for facing this, such as the creation of global policies with a clear environmental guideline. Within these policies, the control of Greenhouse Gase (GHG) emissions has been defined as mandatory, but for carrying out this, a smart strategy is proposed. This is the application of a circular economy model, which seeks to minimize the generation of waste and maximize the efficient use of resources. From this point of view, CO2 recycling is an alternative to reduce emissions to the atmosphere, and we need to look for new business models which valorization this compound which now must be considered as a renewable carbon source. This has renewed the interest in known processes for the chemical transformation of CO2 but that have not been applied at industrial level because they do not offer evident profitability. For example, the methane produced in the Sabatier reaction has a great potential for application, but this depends on the existence of a sustainable supply of hydrogen and a greater efficiency during the process that allows maximizing energy efficiency and thermal control to maximize the methane yield. Regarding energy efficiency and thermal control of the process, the use of structured reactors is an appropriate strategy. The evolution of new technologies, such as 3D printing, and the consolidation of knowledge in the structing of catalysts has enabled the use of these reactors to develop a wide range of possibilities in the field. In this sense, the present review presents a brief description of the main policies that have motivated the transition to a circular economy model and within this, to CO2 recycling. This allows understanding, why efforts are being focused on the development of different reactions for CO2 valorization. Special attention to the case of the Sabatier reaction and in the application of structured reactors for such process is paid

    Structuring Pt/CeO2/Al2O3 WGS catalyst: Introduction of buffer layer

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    This work is devoted to the development of novel structured catalytic system for WGS reaction. The new concept is related to the presence of a pre-catalytic “buffer” layer formed by WGS-inert oxide, i.e. not involved in CO conversion, but able to increase the number of participating sites in water dissociation step during the reaction. The performance of the proposed systems appears to depend strongly on the stream composition, being its effect beneficial in highly reducing atmospheres making it ideal for clean-up application. An increment of the partial kinetic order for water species is observed and reveals the key role of the water activation for superior catalytic behavior.Junta de Andalucía TEP-819

    Au-supported on Fe-doped ceria solids prepared in water-in-oil microemulsions: Catalysts for CO oxidation

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    Gold catalysts were synthesized by deposition-precipitation employing Fe-doped ceria systems, previously obtained by means of the water-in-oil microemulsions methodology with different iron contents (10, 25 and 50 Fe at.%). The final catalysts were tested in the CO oxidation reaction in presence of H2. After gold deposition the crystalline structure of the supports was not altered. Moreover no XRD lines associated to gold were detected, indicating its high dispersion. Solid solution was generated in all samples, although the segregation of iron oxide was detected for the material with the highest iron loading. This phenomenon was then enhanced for the corresponding gold catalyst that also presented sintering of the gold nanoparticles. Strong interaction between gold and the oxygen vacancies of the supports was demonstrated, as well as the promotion of the reducibility of surface Ce4+ and Fe3+ species at low temperatures. A remarkable promotion of the CO conversion at lower temperatures respect to that of the supports was observed for the gold catalysts. Below 120 °C, lower the amount of iron incorporated, higher the catalytic performance of the catalyst. This behaviour is closely related not only to a high gold dispersion but also to the ability for creating additional oxygen vacancies in the support, required for the CO oxidation reaction

    Fe-doped ceria solids synthesized by the microemulsion method for CO oxidation reactions

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    A series of Ce-Fe mixed oxides as well as the pure oxides were synthesized by the microemulsions method. The solid solution formation was established for all the Fe-doped systems and only a hardly noticeable segregation of α-Fe2O3 was appreciated for the solid with the maximum iron content (50at.% Fe). The oxygen exchange is improved for all the Fe-doped systems; however the 10at.% Fe appears as the optimal iron content for achieving the maximum oxygen vacancies concentration and the higher reducibility efficiency. The CO oxidation (TOX, PROX) is especially achieved for the solids with the lower iron contents but with a superior oxygen vacancies proportion. These Ce-Fe systems prepared from microemulsions are very attractive to be considered as supports for depositing active phases capable of enhancing oxygen exchange ability of the whole system, allowing higher CO oxidation abilities.Ministerio de Ciencia e Innovación ENE2009-14522-C05-01Junta de Andalucía P09-TEP-545

    Microreactors technology for hydrogen purification: Effect of the catalytic layer thickness on CuOx/CeO2-coated microchannel reactors for the PROX reaction

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    Two blocks of microreactors composed by 100 microchannels and coated, respectively, with 150 and 300 mg of a CuOx/CeO2 catalyst, were prepared and tested in the preferential oxidation of CO in presence of H2 (PROX). The deposition of different amount of catalyst resulted in different catalytic layer thicknesses thus modifying the catalytic performances of the microreactor. The evaluation of the main reaction variables (the space velocity, the O2-to-CO ratio and the presence of H2O and/or CO2 in the stream) was performed over both microreactors and compared to that of the parent powder catalyst. The least loaded microreactor, with a coating thickness around 10 μm, presented the highest CO conversion and selectivity levels at temperatures below 160 ºC. This result evidences i) the improvement of the catalytic performances got by the structuration of the powder catalyst and ii) the importance of the selection of the adequate thickness of the catalytic layer on the microreactor, which have not to exceed and optimal value. An adequate coating thickness allows minimizing the mass and heat transport limitations, thus resulting in the enhancement of the catalytic performance during the PROX reactionEspana Mineco ENE2012-374301-C03-01 ENE2013-47880-C3-2- RFEDER Junta de Andalucia Unión Europea TEP-819

    Oxidation of CO over gold supported on Zn-modified ceria catalysts

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    A series of Zn-modified ceria solids were prepared by thermal decomposition of the corresponding metal propionates. The formation of segregated ZnO particles on the ceria surface is evidenced for these solids using X-ray diffraction; in addition to this the characterization data may allow discarding the formation of a ZnO¿CeO2 solid solution. On modifying with Zn, the reducibility of the ceria support is enhanced, being the highest reducibility the one obtained for the ZnO¿CeO2 solid having a 1:9 Zn:Ce atomic ratio (CeZn10). The activity of this solid in the CO oxidation reaction was the highest among the tested Zn-modified ceria solids. Therefore, catalysts containing 1 wt.% gold, supported on pure ceria and CeZn solids, were prepared, characterized and their catalytic activities tested. The Zn-modified gold catalyst is more active than the un-modified Au/CeO2 catalyst in the oxidation of CO; this behavior is related to the higher metallic dispersion of gold on the CeZn support surface. However, the number of oxygen vacancies acting as nucleation sites for gold, is hardly modified in the Zn-modified ceria support and, therefore, the higher gold dispersion must be related to high electron density sites on the catalyst surface as a result of Au-Ce-Zn interaction, this improved gold dispersion results in higher activities for CO oxidation.Ministerio de Ciencia e Innovación ENE2009-14522-C05-01Junta de Andalucía P09-TEP-545

    Gold supported on metal-doped ceria catalysts (M = Zr, Zn and Fe) for the preferential oxidation of CO (PROX)

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    A series of ceria oxides doped with 10 mol.% of Zr, Zn and Fe have been prepared by a pseudo sol-gel method throughout the thermal decomposition of the corresponding metallic propionates. With these supports, 1 wt.% gold catalysts were prepared by the deposition-precipitation method. All the solids were characterized by means of XRF, N2 adsorption, XRD, Raman spectroscopy and SEM techniques, and their catalytic activity toward preferential oxidation of CO (PROX) reaction tested. The results showed solid solution when doping with Zr and Fe and ZnO surface segregation in the case of Zn. We demonstrate that gold dispersion depends on not only the oxygen vacancy concentration but also the nature of the doping agent. Finally, the catalytic activity was highly promoted by gold in all cases, being the doped gold catalysts more active than Au/CeO2 at low temperature.Ministerio de Ciencia e Innovación ENE2009-14522-C05-01Junta de Andalucía P09- TEP-545

    Una concepción moderna de Técnicas de Inteligencia Artificial en la Universidad de Alicante

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    Este trabajo tiene como objetivo presentar la estructura de la asignatura Técnicas de Inteligencia Artificial en la Universidad de Alicante haciendo especial hincapié en los recursos (nuevas tecnologías, material docente y aplicaciones software) empleados durante el desarrollo de la misma. Parte de estos recursos docentes están siendo empleados como herramienta de apoyo para la adaptación al Espacio Europeo de Educación Superior
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